Add support for an ERLANG_LIB variable, which will allow repocopied
ports to provide different Erlang runtimes in separate locations.
These will be useful for testing and for running rebar builds without
module conflicts.
No package changes or PORTREVISION bump so far.

* Clean up Java support.
* Use USE_TK.
* Make sure that ODBC is not built if WITHOUT_ODBC is defined.
* Disable ODBC if ${OSVERSION} < 500000.
* Fix pkg-plist using PLIST_SUB.
* Fix some portlint warnings.

Update port to version 8.0 (R8B-0).
Remove my code to handle the documentation merge for patched releases, it
was rather obscure and error-prone. I'll rewrite it in a simpler way next
time I'll need to perform the merge.
Also include a fix for erlang-mode under emacs21 (by Hal Snyder
<hal@vailsys.com> on the erlang mailing list).